Thème Astral
Offers

Open to all

Calculate a birth chart with a simple URL

No form to fill in, no API key, no sign-up. Every chart is described by its address: an AI assistant can build it itself and read the result, as HTML, JSON or plain text.

1. Build a chart's address

Three parameters are enough: the date, the time and the city of birth.

https://monthemesastral.fr/en/birth-chart/result?date=1990-05-12&heure=14:30&ville=Lyon&pays=FR&prenom=Camille

The same chart as JSON (positions, houses, aspects, dominants, links to the interpretation pages), with lang=en for English labels:

https://monthemesastral.fr/api/theme?date=1990-05-12&heure=14:30&ville=Lyon&pays=FR&lang=en

Or as plain text, ready to be read or quoted:

https://monthemesastral.fr/api/theme?date=1990-05-12&heure=14:30&ville=Lyon&format=text&lang=en

2. Accepted parameters

  • date (required): YYYY-MM-DD, from 1900 to 2100.
  • heure (time): HH:MM in the local time of the place of birth (e.g. 14:30). Use unknown if the time is not known: the chart is computed for noon, without Ascendant or houses.
  • ville (city) + pays (two-letter ISO country code, optional): looked up in an offline database of 86,000 cities. For homonyms, the country decides; otherwise the most populated city is kept.
  • lat, lon, tz: alternative to the city. East longitude is positive, west negative. The IANA time zone is derived from the coordinates if absent.
  • maisons (house system): placidus (default), egales (equal houses) or signes-entiers (whole signs).
  • prenom (first name): shown in the chart's title.
  • lang: en for English names, texts and error messages in the API (/api/theme, /api/ciel). The HTML pages use the /en prefix instead.

3. What the JSON returns

The keys are in French and self-explanatory: naissance (input data, UTC, time zone, Julian day), bigThree (Sun, Moon, Ascendant), planetes (longitude, sign, degree, house, retrograde, speed, link to the interpretation page), angles, maisons (houses), aspects (type, orb, applying/separating), dominantes, lune (Moon). With lang=en, names, dates and page links are in English; identifiers (id, signeId, aspectId) stay French. Full specification: /api/openapi.json.

4. The sky today

https://monthemesastral.fr/api/ciel?lang=en
https://monthemesastral.fr/api/ciel?date=2026-10-02&format=text&lang=en
https://monthemesastral.fr/en/sky-today/2026-10-02

4b. Synastry, horoscope and decans

https://monthemesastral.fr/en/synastry/calculator?date1=1990-05-12&heure1=14:30&ville1=Lyon&date2=1992-11-03&heure2=unknown&ville2=Bordeaux
https://monthemesastral.fr/en/horoscope/scorpio · https://monthemesastral.fr/en/horoscope/scorpio/2026-10-05
https://monthemesastral.fr/en/decans?date=1990-05-12 · https://monthemesastral.fr/en/decans/taurus-3
https://monthemesastral.fr/en/synastry/aries-and-scorpio

5. Interpretation pages at predictable addresses

Every position has its page, and its address can be guessed:

  • Planet in sign: /en/moon-in-taurus, /en/venus-in-scorpio, /en/leo-rising
  • Planet in house: /en/mars-in-7th-house
  • Sun and Ascendant: /en/aries-sun-leo-rising
  • Aspects: /en/aspects/mars-square-saturn (fastest planet first: sun, moon, mercury, venus, mars, jupiter, saturn, uranus, neptune, pluto; aspects: conjunction, sextile, square, trine, opposition)

Planet slugs in English URLs: sun, moon, mercury, venus, mars, jupiter, saturn, uranus, neptune, pluto, north-node, chiron, lilith. Signs: aries, taurus, gemini, cancer, leo, virgo, libra, scorpio, sagittarius, capricorn, aquarius, pisces. In the JSON, identifiers remain French (soleil, lune, mercure, venus, mars, jupiter, saturne, uranus, neptune, pluton, noeud-nord, chiron, lilith; belier, taureau, gemeaux, cancer, lion, vierge, balance, scorpion, sagittaire, capricorne, verseau, poissons).

6. Precision and method

Apparent geocentric positions referred to the ecliptic and equinox of date (tropical zodiac), computed from the VSOP87 (planets) and ELP (Moon) astronomical models and JPL ephemerides for Chiron, with arc-minute precision. True lunar node, mean Lilith. Local time → UTC conversion with the complete time-zone history (daylight saving, wartime). Placidus houses (equal houses beyond 66° of latitude).

7. Terms of use

Free, open access for reasonable use, with attribution to the source (monthemesastral.fr). A /llms.txt file summarises this information for agents.